Often shock absorbers are designed such that the damping rate of the shock absorber becomes higher at the extreme ends of the rebound and compression strokes. The additional damping is desired to prevent an abrupt halt to the piston stroke and to prevent jarring metal-to-metal contact between the various parts in the shock absorber. A variety of mechanisms have been devised to render a higher damping rate at the two extremes. Springs and elastomeric jounce bumpers have been incorporated internally as well as externally of the working cylinder. In addition, secondary pistons have been used which become operative only at the extreme ends of the piston stroke. All previous mechanisms added to the cost of the shock absorber.
It is desired to have a hydro-mechanical stop which effectively dampens the end of a piston stroke while being economical to manufacture and assemble.